1. Field of the Invention
This invention relates to the field of optoelectronic devices. More specifically, this invention relates to an X-Y array, or network, of pnpn solid state light sensitive devices. Each row and each column of the light sensitive devices are connected in parallel, and to a load resistor to form a Winner-Take-All (WTA) type of maximum illumination detector. In such an arrangement, activation of one device prevents any other device from subsequently being activated.
2. Description of Prior Art
In many optical signal and image processing systems, such as optoelectronic computers, optical communication systems, correlators and optoelectronic fuzzy logic systems, it is important to identify the physical location of a maximum intensity optical signal; that is, the physical location of the brightest light spot within a field of view comprising, for example, the viewing of an image that comprises an input image projected onto an array of X-Y pixels. In some cases, it is also desirable to sense the intensity of the brightest spot.
A conventional way to perform this function is to use sensor arrays and multiplexers to convert the input light image into a serial train of electrical signals that are then converted into digital data. This data is then fed into a digital computer to calculate the position of the maximum intensity spot in the input image. The present invention generates the desired maximum intensity spot data directly within the array by the use of an optoelectronic winner-take-all network.
The general concept of providing a signal output that is modified as the result of the maximum/minimum values of a signal input is known in the art. For example, U.S. Pat. No. 4,975,773 provides that an input video signal is black level expanded only when there is a dynamic range to the range of the input video signal; i.e., when the input video signal's integrated minimum value is less than a predefined limit value. When black level expansion occurs (i.e., when the input video signal's integrated minimum value is equal to or greater than the predefined limit value), the input video signal is black level expanded in a manner that considers both the video signal's integrated minimum value and the video signal's integrated maximum value.
Other concepts that involve identifying maximum amplitude signals include U.S. Pat. No. 4,908,872 which describes apparatus for extracting pattern contours from the X-Y coordinate image data that is provided by a TV camera. In this device, each image pixel has a gray level magnitude and direction, these two characteristics of a pixel defining its gray level vector. Adjacent pixels that have a direction in a defined X direction are grouped together, as are adjacent pixel having a direction in a defined Y direction. The maximum magnitude pixel for the X direction group and the maximum magnitude pixel for the Y direction group are then summed to define the pattern contour of the TV image.
The use of solid state light sensors that are connected in a winner-take-all configuration, and are operable to detect the location of maximum light intensity is suggested in the publication OPTOELECTRONICS-Devices and Technologies, Vol. 5, No. 2, pp. 311-315, December 1990.
The present invention relates to devices of the latter type wherein new and unusual electrical means are provided to read out the location of maximum light intensity within an input image comprising an X-Y matrix of light pixels, and to read out the magnitude of this maximum light intensity.